1. Field of the Invention
The present invention relates to an IP telephone apparatus that can be applied to an IP telephone system utilizing ENUM (tElephone NUmber Mapping) technology.
2. Description of Related Art
Today, it is becoming possible to utilize a plurality of communication methods in order to contact a call destination via a communication network. For example, it is possible to communicate with a call destination by one of such access methods as ordinary telephones, IP telephones, facsimiles, e-mails and cellular phones. It means that one user has a plurality of call destination's numbers such as regular telephone numbers (including fax telephone numbers), IP telephone numbers, e-mail addresses and cellular phone numbers. There is also a case where one user has a plurality of telephone numbers and e-mail addresses. Therefore, a calling user establishes a connection with a communication apparatus of a call destination by inputting, to the calling user's communication apparatus, one of the call destination's telephone numbers in accordance with the selected access method.
As described above, when one user has a plurality of call destination's numbers, even when a call is placed to an IP telephone number of the call destination and the line is busy, it is possible to call back a different number of the call destination (e.g., regular telephone number).
Moreover, some IP telephone apparatuses have not only IP telephone functions that enable voice communication via an IP network but also have telephone functions that enable voice communication via PSTN (Public Switched Telephone Network) (See Related Art 1, for example). One communication apparatus has a plurality of access methods to select from (IP and ordinary telephones).
[Related Art 1] Japanese Patent Laid-Open Publication 2004-248086
However, conventional IP telephone apparatuses require users to check a regular telephone number of the call destination and call back that telephone number when an IP telephone number of the call destination is called and the line is busy. In other words, although it is possible to use a plurality of access methods, when the line is busy, users need to input, to a communication apparatus, a different number of the call destination in order to re-access by switching to a different access method.